Fog in Dulles, VA

daily fog outlook & 2016–2026 climatology
No fog signal in NWS guidance for the next 48 hours. dense fog (visibility under a mile) is rare here in August.forecast cycle 2026-08-16T00:00:00Z · page rebuilt daily · live layers below update hourly

Measured at Washington Dulles International Airport (KIAD). This station is in forecast verification — percentages publish when it clears the accuracy bar.

Measuring station

stationairportfog hours/yrforecast
KIADWashington Dulles International Airport32 h/yrverifying

Fog is measured where instruments live — airports. Hours/yr = time below CAT I approach minima (visibility under ~½ mile or ceiling under 200 ft), the aviation definition of seriously dense fog.

When Dulles fogs in

Fog here concentrates in January and December — about 32 hours in a typical year at KIAD, usually lasting ~2 h once it forms. Hour-by-hour patterns, live conditions and the forecast strip live on the KIAD station page.

Fog season

January: ~8 hJanFebruary: ~5 hFebMarch: ~3 hMarApril: ~0 hAprMay: ~1 hMayJune: ~1 hJunJuly: ~0 hJulAugust: ~0 hAugSeptember: ~1 hSepOctober: ~3 hOctNovember: ~2 hNovDecember: ~7 hDec
Fog season runs October through March, peaking in January; fog is mostly a 5 AM–9 AM phenomenon; typically thinning out by 11 AM; a typical event lasts about 2 hours once it forms local time · 10-yr average

Machine access: data.json · llms.txt · forecast verification. Not for operational use.